Anti-corrosion and anti-erosion protective layer containing aluminium

ABSTRACT

The corrosion and also the erosion properties of a layer system can be improved by using deposition-hardened particles.

The invention relates to an aluminum-containing protective layer to protect against corrosion and erosion.

Compressor blades of stationary GTs and aircraft turbines are usually produced on the basis of heat-treated martensitic 12%-13% Cr steels and sometimes of precipitation-hardened 16%-17% Cr steels. As protection against corrosion, the blades of the front stages are protected by means of a special aluminum pigment-containing high-temperature surface coating.

The disadvantage of this coating is the relatively low erosion resistance of the layer. As a consequence thereof, not only a very complicated filtering of the air but often also a regular recoating of the blades (in the course of refurbishment) are necessary.

To solve this problem, the protective layers used to date are inspected at regular intervals for erosion damage and corrosion protection and in the course of refurbishment removal of the coating with subsequent recoating of the blades with the same system are carried out. The length of these time intervals is greatly dependent on the ambient air and the effectiveness of filter devices.

This problem is to be solved.

The object is achieved by a layer system as claimed in claim 1.

The refurbishment intervals could be lengthened by increasing the erosion resistance of the coating.

In the dependent claims, further advantageous measures which can be combined with one another in any way to achieve further advantages are listed.

FIGS. 1-28 show layer systems.

The figures and the description present only examples of the invention.

FIG. 1 shows a layer system 1 made up of a substrate 4 with a single layer 7 which contains soft aluminum particles Al having a hardness of ≦Hv50.

Preference is given to the harder aluminum-containing particles AL* in a layer 7′ (FIG. 11).

The single layer 7″ can, proceeding from FIG. 1, preferably additionally comprise hard material particles (H), as shown in FIG. 5.

This likewise applies to a single layer 7′″ as per FIG. 13 proceeding from FIG. 11.

FIG. 2 shows a layer system 1 made up of a substrate 4 with a double protective layer 7, 10 to protect against corrosion and erosion (corresponds to FIG. 1+outer layer 10). According to this prior art, the layer 7, which is located directly on the steel-containing substrate 4, comprises soft aluminum particles Al and acts as sacrificial anode, whereas the upper layer 10 does not comprise any aluminum particles. In FIG. 2, the soft aluminum particles Al are present in the lower layer 7 and the upper layer 10 does not comprise any particles but only a matrix material.

FIG. 8 shows FIG. 2 for harder aluminum-containing particles AL* in the lower layer 7′.

To increase the erosion resistance, proceeding from FIG. 2 or FIG. 8, exclusively hard material particles H can be present only in the outer layer 10″, as shown in FIG. 4 and FIG. 6.

A further example of the invention comprises introducing aluminum into both layers (FIG. 3), with softer aluminum particles Al (“pure” aluminum) being present in the lower layer 7 and harder aluminum-containing particles AL* being present in the upper layer 10′, however.

Depending on the field of application, hard material particles H can be incorporated in the lower layers 7″ and 7″′ and in the upper layer 10′, 10″ as per FIG. 7 proceeding from FIG. 2 and as per FIG. 10 (proceeding from FIG. 8) or only in the upper layer 10″ (FIG. 4, 6) or, as per FIG. 9 proceeding from FIG. 8 and as per FIG. 12 proceeding from FIG. 2, only in the lower layer 7″′, 7″.

In addition, the upper layer can be provided with soft aluminum particles Al, harder, aluminum-containing particles AL* and/or hard material particles H or the upper layer 10 ^(IV) can comprise only soft aluminum particles composed of aluminum or the upper layer 10 ^(V) comprises both hard material particles H and relatively hard aluminum-containing particles AL*.

In FIG. 14, the lower layer 7 comprises soft aluminum particles Al and the upper layer 10″′ likewise but also hard material particles H as erosion protection.

In FIG. 15, both the lower layer 7 and the upper layer 10 ^(IV) comprise aluminum particles, with the aluminum particles being utilized in the outer layer 10 ^(IV) to increase erosion protection even though they give less erosion protection than hard material particles.

In FIG. 16, the lower layer 7 comprises soft aluminum particles Al and the upper layer 10 ^(V) comprises harder aluminum-containing particles AL* and hard material particles H.

Proceeding from FIG. 3, FIG. 17 does not comprise any aluminum particles but instead harder aluminum particles AL* in the lower layer 7′.

FIG. 18 shows a lower layer 7′ comprising relatively hard aluminum-containing particles AL*, on top of which an upper layer 10′″ comprising soft aluminum particles Al and hard material particles H has been applied.

In FIG. 19, the lower layer 7′ comprises relatively hard aluminum-containing particles AL* which contribute to erosion protection when the upper layer 10 ^(IV) has been removed since the upper layer 10 ^(IV) contains only aluminum particles.

The hardest erosion protection is formed by an upper layer 10 ^(V) in which relatively hard aluminum particles AL* and hard material particles are present, with, depending on the field of application and degree of erosion protection, relatively hard aluminum particles AL* being present in the lower layer 7′ (FIG. 20) or hard material particles being additionally present in the lower layer (FIG. 28).

In FIGS. 21-24, the lower layer 7″ comprises aluminum particles and hard material particles H in order to increase the erosion resistance of the lower layer 7″.

In FIG. 21, relatively hard aluminum-containing particles AL* are present in the upper layer 10′ in order to contribute both to corrosion protection and to erosion protection.

In FIG. 22, this is achieved by means of soft aluminum particles Al and hard material particles H in the upper layer 10′″.

In less erosive environments, the upper layer 10 ^(IV) can, in comparison to FIG. 22, also comprise only aluminum particles (FIG. 23).

In particular, the outer layer is protected against erosion by the upper layer 10 ^(V) comprising aluminum-containing relatively hard particles AL* and hard material particles H (FIG. 24).

In FIGS. 25-28, the lower layer 7″′ comprises relatively hard aluminum-containing particles AL* and hard material particles H in order to protect the substrate 4 against erosion in any event, with relatively hard aluminum-containing particles AL* being present in the upper layer 10′ in FIG. 25 and erosion protection also however being ensured by hard material particles in the aluminum-containing layer 10″′ in FIG. 26.

FIG. 27 shows an upper layer 10 ^(IV) which comprises soft aluminum particles Al and also contributes, in particular, to corrosion protection and only when the upper layer has been removed does the lower layer ensure both corrosion protection and erosion protection.

As hard material particles H, it is possible to use ceramic particles, preferably aluminum nitride and boron nitride, chromium carbide, aluminum oxide or mixtures thereof.

The substrate 4 (FIGS. 1-28) preferably comprises a steel.

The increase according to the invention in erosion protection is achieved by use of relatively hard, aluminum-containing particles AL* composed of an aluminum alloy, in particular a precipitation-hardened aluminum alloy, which has a 5-10-fold greater hardness and a strength which is higher by a factor of at least 5.

As precipitation-hardening alloys composed of aluminum and at least one element from the group consisting of Zn, Mg, Cu, Mn, Co, preference is given to using, in particular, the following alloys: Al—Zn, Al—Zn—Mn, Al—Mn—SC, Al—Mg—Mn, Al—Mg—Zn—Cu, Al—Cu—Mn—Zn, AlZn4.5Mg1, AlZnMgCu1.5, AlZnMgCu0.5, AlMg4.5Mn.

However, it is also possible to employ alloys having significantly higher contents of various alloying elements, e.g. having 6%-8% of zinc (Zn).

Preference is likewise given to using:

-   -   particles AL* composed of aluminum composites made up of         aluminum or an aluminum alloy as matrix: Al—Si, Al—Si—Mg, Al—Mn,         Al—Fe, Al—Ni, Al—Zn with an incorporated second component such         as ceramic particles composed of Al₂O₃ or SiC,     -   dispersion-hardening aluminum materials comprising oxides,         carbides or nitrides (Al₂O₃, Al₄C₃), comprising lithium (Li) or         using intermetallic phases: AlFe₈₃Co, AlFe₈Ce₄, AlFe₈Zr₁,     -   aluminides: in particular NiAl, Ni₃Al, FeAl, Fe₃Al, TiAl, Ti₃Al,     -   precipitation-hardening scandium-containing (Sc) aluminum alloys         Al—Sc or Al—Sc—X alloys.

After baking of the aluminum pigment layer, a conductivity blasting with low intensity is generally carried out. Targeted pressure blasting using optimized parameters enables a high increase of aluminum particles to be additionally achieved.

The matrix material of the layers 7, 7′, 7″, 7″′, 10, 10′, 10″, 10″′, 10 ^(IV), 10 ^(V) (FIGS. 1-28) is preferably a chromate-phosphate binder and is preferably the same for both layers. 

1. A layer system which comprises at least: a substrate; a lower layer of a matrix material on the substrate; optionally an outer layer of a matrix material on the lower layer; wherein particles composed of aluminum (Al) having a soft hardness, are present in the matrix material of at least one of the layers of the layer system; at least one of the layers includes in the matrix material thereof aluminum-containing particles (AL*) which are harder than the soft hardness particles composed of aluminum (Al) wherein the aluminum-containing particles (AL*) comprise an aluminum alloy or a precipitation-hardening aluminum alloy having a hardening mechanism, and the precipitation-hardening aluminum-containing particles (AL*) comprise an alloy of aluminum-zinc (Al—Zn); aluminum-zinc-manganese (Al—Zn—Mn); aluminum-manganese-scandium (Al—Mn—Sc); aluminum-magnesium-manganese (Al—Mg—Mn); aluminum-magnesium-zinc-copper (Al—Mg—Zn—Cu); aluminum-magnesium-zinc-copper-cobalt (Al—Mg—Zn—Cu—Co); and aluminum-copper-manganese-zinc (Al—Cu—Mn—Zn)
 2. (canceled)
 3. The layer system as claimed in claim 1, wherein the aluminum-containing particles (AL*) comprise scandium-containing (Sc) aluminum Al alloys: Al—Sc, Al—Cu—Sc, Al—Si—Sc, Al—Mg—Si—Sc, Al—Zn—Mg—Sc, Al—Li—Sc and/or Al—Mg—Sc.
 4. The layer system as claimed in claim 1, wherein dispersion-hardening aluminum alloys are used for the aluminum-containing particles (AL*), wherein the aluminum-containing particles (AL*) are produced by mechanical alloying.
 5. The layer system as claimed in claim 1, wherein the aluminum-containing particles (AL*) are selected from aluminides NiAl, Ni₃Al, FeAl, Fe₃Al, TiAl, Ti₃Al, AlFe₈, AlFe₈Co, AlFe₈Ce₄ and/or AlFe₈Zr₁.
 6. The layer system as claimed in claim 1, wherein the aluminum-containing particles (AL*) comprise aluminum composites selected from: aluminum (Al), an aluminum alloy, selected from alloys Al—Si, Al—Si—Mg, Al—Mn, Al—Fe, Al—Mn—Fe, Al—Ni, Al—Zn, and having an incorporated harder ceramic component which includes oxides or nitrides.
 7. The layer system as claimed in claim 1, having a lower layer and no outer layer outward of the lower layer; and the lower layer having particles of aluminum selected from aluminum alloy and having hard particles not of aluminum.
 8. The layer system as claimed in claim 1, which comprises at least: only one lower layer; and only one outer layer.
 9. (canceled)
 10. the layer system as claimed in claim 1, further comprising hard material particles (H) or (AL*) present in the lower layer.
 11. The layer system as claimed in claim 1, further comprising hard material particles (H) present in the upper layer along with the aluminum particles.
 12. The layer system as claimed in claim 1, further comprising hard material particles (H) present in both layers.
 13. The layer system as claimed in claim 1, further comprising hard material particles in at least one of the layers and comprising at least one of aluminum nitride, boron nitride, chromium carbide, aluminum oxide or mixtures thereof
 14. The layer system as claimed in claim 1, wherein each of the layers or both of the layers are comprised of the same matrix material, in which the particles are included.
 15. (canceled)
 16. The layer system as claimed in claim 1, wherein the substrate is comprised of a steel.
 17. The layer system as claimed in claim 1, wherein the aluminum particles have an increased hardness as a result of production thereof including conductivity blasting.
 18. The layer system as claimed in claim 7, wherein the lower layer comprises aluminum particles (Al) having a maximum hardness of Hv50, and the upper layer comprises aluminum particles having an at least 10% greater hardness (AL*), wherein precipitation-hardening aluminum alloy particles (AL*) are in the upper layer.
 19. The layer system as claimed in claim 1, wherein the upper layer does not comprise any aluminum-containing particles (AL*) or aluminum particles (Al).
 20. The layer system as claimed in claim 1, wherein the lower layer is directly on the substrate.
 21. The layer system as claimed in claim 1, wherein the soft hardness of the aluminum particles soft hardness is up to Hv50.
 22. The layer system as claimed in claim 1, wherein the alloy includes: Al₃Li and/or AlZn4.5Mg1 and/or AlZnMgCu1.5 and/or AlZnMgCu0.5 and/or AlMg4.5Mn.
 23. The layer system as claimed in claim 5, wherein the harder ceramic component includes Al₂O₃, Al₄C₃ and/or SiC
 24. The layer system as claimed in claim 17, wherein the conductivity blasting comprises cold strengthening processes, particle blasting or rolling.
 25. A layer system comprising: a substrate; a lower covering layer on the substrate made of a first matrix material; an outer layer on the lower layer and made of a second matrix material; the outer layer includes in the second matrix material of the outer layer at least one of aluminum particles and hard aluminum particles and the outer layer optionally includes hard particles not of aluminum.
 26. The layer system as claimed in claim 2, wherein the lower layer includes at least one of particles of aluminum, hard aluminum and hard particles not of aluminum. 